The invention relates to electrical connectors and, more specifically, to ball grid array connectors having a plurality of solder balls for surface mounting that are connected to pin grid arrays.
Japanese Unexamined Patent Publication No. 2000-357572 discloses an integrated circuit (IC) package connector having a ball grid array connector. The connector has a base housing with a plurality of contacts arranged in a matrix, and a sliding cover housing with openings corresponding to the contacts. The contacts are connected to a printed circuit board via solder balls or tines. The IC package has a pin grid array mounted on the cover housing. The pins serve as electrodes and are connected to the contacts on the base housing. Because the IC package has an extremely large number of pins, the connection resistance between the pins and the contacts is great. Therefore, after the pins are inserted within the openings of the cover housing, the cover housing with the IC package mounted thereon is slid by a power assist mechanism to electrically connect the contacts and the pins.
The power assist mechanism has a drive mechanism that acts like a lever provided at an end portion of the connector. Because a large amount of force is required to slide the cover housing to electrically connect the pins and the contacts, the drive mechanism is operated by a tool, such as, a screwdriver. Metal parts are commonly used for the operating parts of the drive mechanism for durability.
In the aforementioned connector, the center of gravity of the connector is biased due to the existence of the drive mechanism, which utilizes heavy metal parts, at the end portion of the connector. In other words, the center of gravity of the connector is at a position biased towards the drive mechanism side, as opposed to the center of the soldering region of the contacts that are soldered to the circuit board.
Due to the positional misalignment between the center of the soldering region and the center of gravity of the connector, during reflow soldering of the connector to the circuit board, the heavier drive mechanism side may be caused to rotate toward the circuit board causing the lighter connector end portion on the opposite side to separate from the circuit board. As a result, the connector may be mounted to the circuit board at an inclination causing electrical connection failure.
In addition, there are cases in which the circuit board undergoes a second reflow soldering process to mount electronic parts on an upper surface of the circuit board opposite of the connector. In this process, the connector that has already been soldered to the circuit board is suspended on the circuit board while the electronic parts are mounted on the upper surface of the circuit board. As the atmospheric temperature near the circuit board rises, the soldering portions between the connector and the circuit board soften and melt. Generally, the soldered portions that melt remain mounted to the circuit board due to surface tension. However, if the center of gravity of the connector is positionally misaligned from the center of the soldering region, a rotational movement is generated by the weight of the drive mechanism so that the end portion on the drive mechanism side separates from the circuit board causing the connector to become inclined with respect to the circuit board, fixing the connector to the circuit board in an inclined state. In this state, there is a possibility that electrical connections will fail or that the connector will detach from the circuit board.
In addition, there are cases in which a heat sink is mounted on the IC package to dissipate heat. The heat sink is mounted parallel to the circuit board. A problem darises in that the heat sink does not appropriately contact the inclined surface of the IC package mounted on the inclined connector such that sufficient heat dissipation is not obtained. Because computer central processing units (CPU) operate at high speeds and generate a high amount of heat, if the heat dissipation is insufficient there is a possibility that it will negatively effect the operation of the CPU.
It is therefore desirable to provide a ball grid array connector that enables reflow soldering of the connector parallel to a circuit board, even in cases where the center of gravity of a housing assembly is positionally misaligned with the center of the soldering region. It is further desirable to provide a ball grid array connector to which a circuit board mounted type heat sink is attachable to obtain sufficient heat dissipation.
This and other objects are solved by an electrical connector having an insulative housing with a plurality of contacts in electrical connection with corresponding solder balls that protrude from a surface of the housing. The solder balls form a soldering region for attachment to a circuit board. The housing has a center of gravity biased from a center of the soldering region, and a positional compensation member is attached to the housing and the circuit board. The positional compensation member prevents the housing from becoming inclined with respect to the circuit board when the solder balls are attached to the circuit board and prevents the housing from becoming inclined with respect to an electronic part when the electronic part is mounted to the housing on a side opposite from the circuit board.